Transcript Introduction to Electrical Drives By Dr. Ungku Anisa Ungku Amirulddin Department of Electrical Power Engineering College of Engineering Dr.

Introduction to Electrical Drives
By
Dr. Ungku Anisa Ungku Amirulddin
Department of Electrical Power Engineering
College of Engineering
Dr. Ungku Anisa, July 2008
EEEB283 - Electrical Machines & Drives
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Definition of Electrical Drives
 Drives – system employed
for motion control
Drives -> Motion Control
 Motion control requires
prime movers
Prime Mover
 Electrical Drives – Drives
that employ Electric
Motors as prime movers
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EEEB283 - Electrical Machines & Drives
Electrical Drives -> Electric
Motor as Prime Mover
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Conventional Electric Drives
 Disadvantage :
 Bulky
 Expensive
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 Inefficient
 Complex
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Modern Electric Drives
Power Source
Power Processing Unit
Motor
Load
feedback
Control
Control
Reference
Unit
 Small
 Flexible
 Efficient
 Interdisciplinary
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Electric Drives Application
 Line Shaft Drives
 Oldest form
 Single motor,
multiple loads
 Common line
shaft or belt
 Inflexible
 Ineffcient
 Rarely used
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Electric Drives Application
 Single-Motor, Single-
Load Drives
 Most common
 Eg: electric saws,
drills, fans, washers,
blenders, diskdrives, electric cars.
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Electric Drives Application
 Multimotor Drives
 Several motors,
single mechanical
load
 Complex drive
functions
 Eg: assembly
lines, robotics,
military airplane
actuation.
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Basic Components of Electric
Drives
Power
Processing Unit
Power Source
Control
Control
Reference
Motor
Load
feedback
Unit
 Motor
 Power Processing Unit (Electronic Converter)
 Control Unit
 Power Source
 Mechanical Load
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Basic Components of Electric
Drives - Motor
• DC motors - Permanent Magnet or wound-field (shunt,
separately excited, compound, series)
• AC motors – Induction, Synchronous (wound –rotor,
IPMSM, SPMSM), brushless DC
• Selection of machines depends on many factors, e.g.:
• application
• cost
• efficiency
• environment
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Basic Components of Electric
Drives – Power Source
• Regulated (e.g: utility) or Unregulated (e.g. : renewable
energy)
• DC source
• Batteries
• fuel cell
• photovoltaic
• AC source
• Single- or three- phase utility
• wind generator
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EEEB283 - Electrical Machines & Drives
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Basic Components of Electric
Drives – Power Processing Unit
• Provides a regulated power supply to motor
• Combination of power electronic converters
 Controlled rectifiers, inverters –treated as ‘black boxes’
with certain transfer function
More efficient
Flexible
Compact
AC-DC , DC-DC, DC-AC, AC-AC
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Basic Components of Electric
Drives – Power Processing Unit
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Basic Components of Electric
Drives – Power Processing Unit
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Basic Components of Electric
Drives – Control Unit
• Supervise operation
• Enhance overall performance and stability
• Complexity depends on performance requirement
• Analog Control – noisy, inflexible, ideally infinite bandwidth
• Digital Control – immune to noise, configurable, smaller
bandwidth
• DSP/microprocessor – flexible, lower bandwidth, real-time
• DSPs perform faster operation than microprocessors
(multiplication in single cycle), can perform complex
estimations
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Basic Components of Electric
Drives – Mechanical Load
• Wide variation of Torque-speed (T-) characteristics
• Load torque is function of speed
• T  k
where k = integer or fraction
L
m
• Mechanical power of load:
2
•
and  m 
P  T L m
nm
60
Angular speed
in rad/s
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Speed
in rpm
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Basic Components of Electric
Drives – Mechanical Load
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Basic Components of Electric
Drives – Mechanical Load
 Torque independent
of speed , k = 0
 Hoist
 Elevator
 Pumping of water
or gas against
constant pressure
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Basic Components of Electric
Drives – Mechanical Load
 Torque proportional
to square of speed ,
k=2
 Fans
 Centrifugal pumps
 Propellers
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Basic Components of Electric
Drives – Mechanical Load
 Torque inversely
proportional to
speed , k = -1
 Milling machines
 Electric drill
 Electric saw
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Torque Equation for Rotating
Systems

TL
Te  T L 
d  J m 
Te , m
dt
J
With constant J,
Te  T L  J
•
•
d  m 
d 
2
 J
dt
dt
2
First order differential equation for angular frequency (or velocity)
Second order differential equation for angle (or position)
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Torque Equation for Rotating
Systems with Gears
 Low speed applications use gears to utilize high speed
motors
m1
m
Motor
Te
N1
Load 1,
TL1
m2
J1
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EEEB283 - Electrical Machines & Drives
N2
J2
Load 2,
TL2
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Torque Equation for Rotating
Systems with Gears
m1
m
J equ  J 1  a J 2
2
2
Motor
Te
N1
Load 1,
TL1
J2
TLequ = TL1 + a2TL2
N2
J1
Load 2,
TL2
a2 = N1 / N2
Motor
Te
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EEEB283 - Electrical Machines & Drives
m
Jequ
Equivalent
Load , TLequ
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Steady State Motor T-
Characteristic
SPEED
Synchronous motor
Induction motor
Series DC motor
Separately excited
/ shunt DC motor
TORQUE
By using power electronic converters, the motor
characteristic can be varied
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EEEB283 - Electrical Machines & Drives
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Steady State Motor and Load
T- Characteristic
• At constant
speed, Te= TL
• Steady state
Torque
Te
speed is at
point of
intersection
between Te
and TL of the
steady state
torque
characteristics
Dr. Ungku Anisa, July 2008
TL
Steady state
Speed, r
r3
EEEB283 - Electrical Machines & Drives
r1
r2
Speed
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Torque-Speed Quadrant of
Operation 
m
Te
m
Te
• Direction of positive (forward)
speed is arbitrary chosen
• Direction of positive torque will
produce positive (forward) speed
Quadrant 2
Forward braking
Quadrant 1
Forward motoring
Quadrant 3
Reverse motoring
Quadrant 4
Reverse braking
Te
m
Dr. Ungku Anisa, July 2008
EEEB283 - Electrical Machines & Drives
T
Te
m
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References
 El-Sharkawi, M. A., Fundamentals of Electric Drives,
Brooks/Cole Publishing Company, California, 2000.
 Krishnan, R., Electric Motor Drives: Modelling, Analysis and
Control, Prentice-Hall, New Jersey, 2001.
 Nik Idris, N. R., Short Course Notes on Electrical Drives,
UNITEN/UTM, 2008.
 Ahmad Azli, N., Short Course Notes on Electrical Drives,
UNITEN/UTM, 2008.
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